1. Field of Invention
This invention relates generally to the treatment of settled wastewater, and in particular to efficiently treating the water flowing from an on-site treatment process such as a septic tank by mechanical removal and biological conversion in a multi-chambered tank containing various media.
2. Description of Prior Art
Common subsurface wastewater disposal systems are designed with septic tank effluent flowing to some form of a soil absorption disposal area as regulated by local or State Health Codes.
Various types of filters and treatments have been offered in the art to provide some form of filtering or pre-treatment of wastewater prior to final disposal to a subsurface wastewater disposal system. Supplemental treatment to wastewater is provided in efforts to assure environmental sanitation and improve the quality of effluent which eventually enters the groundwater and surface waters.
There have been inventors proposing revisions to septic tanks. U.S. Pat. No. D371,423 to Salagnac (1996) discloses an aesthetic shaped septic tank. U.S. Pat. No. 4,997,564 to Warner (1989) improved the efficiency of the septic tank by adding multiple compartments. This design utilizes multi compartments but they are installed inside a septic tank without filter media or providing an aerobic environment.
U.S. Pat. No. 5,766,454 by Cox et al (1996) proposed home wastewater treatment and denitrification systems utilizing a separate aerobic and anaerobic tank for denitrification. This design teaches away from this invention and requires a mechanical pump for stirring of the wastewater to produce denitrification. U.S. Pat. No. 5,496,472 by Slack et al (1996) was directed at a method and application for denitrification using a weir block and laminal flow. This patent is designed to convey water through a weir and along a wall of a denitrifying vessel.
Several inventions proposed septic tank filters to be placed inside the septic tank to improve wastewater quality, U.S. Pat. No. 5,482,621 to Norse (1994), U.S. Pat. No. 5,635,064 to Bovington (1995), and U.S. Pat. No. 5,683,577 to Norse (1996).
Several inventions have proposed sand filter designs for wastewater effluent management; U.S. Pat. No. 5,667,670 to Drewey (1996) and U.S. Pat. No. 5,770,071 to Drewey (1996), and U.S. Pat. No. 4,100,073 to Hopcroft (1976) proposed a sand filter designed for discharge to surface water bodies.
U.S. Pat. No. 5,618,431 to Kondo et al (1996) proposed a method of preparing and cleaning floating filter medium for a biological cleaning apparatus.
There has been work, in the art, of an anaerobic/aerobic filter plant that is intended for use between a septic tank and a drain field and includes a filter tank that receives effluent from a septic tank. U.S. Pat. No. 4,895,645 to Zorich, Jr. (1997) proposed a filter tank containing aerobic and anaerobic treatment environments. This unit relies on a mechanical pump for circulation and recirculation and does not utilize multi-compartmental design.
The object of my invention is to provide a filter to be utilized between a septic tank and drain field, which will reduce the wastewater strength (i.e., total settleable solids, biochemical oxygen demand, fecal coliform, and total nitrogen) going to the drain field which will either allow for the drain field to be decreased in size or provide a safety factor to reduce failure risk, or improve wastewater quality discharged to the soil, groundwaters, and surface waters.
The filter is relatively compact compared to a conventional sand filter and reduces biochemical oxygen demand, total suspended solids, nitrogen and fecal coliform prior to effluent entering the drain field. The unit elongates the pathway of wastewater flow through several downflow and upflow anaerobic columns and downflow aerobic column of varying filter media. It does not require mechanical devices, however, a pump can be added to recirculate the water if a higher level of wastewater treatment is required.